Wurtz Reaction: Definition, Mechanism, Fittig Reaction & Examples

Wurtz reaction is an organic chemical reaction used to produce alkanes in laboratories along with a halogen and a compound containing sodium. It is a coupling reaction of two haloalkanes with sodium metal in the presence of dry ether. Wurtz reaction is one of the first-named reactions in Organic Chemistry. The chemical reaction is referred to as Wurtz-Fittig reaction when aryl halide is used in the place of alkyl halide, thereby changing the nature of reaction.

• The Wurtz reaction is named after Charles Adolph Wurtz, who provided experimental proof of the Wurtz reaction in the year 1855.
• Sir Charles Adolph Wurtz is also credited with the discovery of the aldol condensation reaction in organic chemistry.
• Wurtz reaction has many applications in the field of Organic Chemistry and organometallic chemistry.
• This type of chemical reaction generally fails when tertiary alkyl halides are used.

Key Terms: Wurtz Reaction, Haloalkanes, Organometallic Chemistry, Alkyl Halides, Wurtz Fittig Reaction, Alkanes, Organic Chemistry, Aldol reaction, Ether  

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What is Wurtz Reaction?

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Wurtz reaction is named after the French Chemist Charles Adolphe Wurtz, who also discovered the aldol reaction. In the Wurtz reaction, two alkyl halides (Haloalkanes) react with sodium metal in the presence of dry ether to produce higher alkanes.

• In place of sodium metal, other elements such as activated copper, zinc, iron, silicon, or indium can also be used.
• Wurtz reactions can take place in a dry environment only.
• Sodium reacts with oxygen and moisture vigorously, thus an anhydrous condition is required.
• Sodium cannot be placed in a standard atmosphere because of its high reactivity, so it is placed inside kerosene.
• In place of anhydrous ether, tetrahydrofuran can also be used. 
• This reaction uses alkyl free radical containing unpaired electrons in the outer shell to form alkanes.
• In the Wurtz reaction, free radicals are used as catalysts resulting in the formation of alkene as a by-product.

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Wurtz Reaction Equation

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The general form of the Wurtz reaction equation can be written as follows:

2R-X + 2Na → R-R + 2Na⁺ X^–

We can observe from the given equation that the two R groups are joined to produce an alkane with a longer chain along with NaX, where X is a Halogen.

Conditions for Wurtz Reaction

In the Wurtz reaction, alkyl halides and sodium metal react in a dry ether solvent to produce alkanes, usually symmetrical alkanes. Due to the formation of multiple byproducts, this reaction is not appropriate for the preparation of unsymmetrical alkanes. The two most important conditions for the Wurtz reaction to occur are:

• To initiate the reaction and maintain the necessary conditions, the reaction is usually carried out under mild heating.
• Excessive heating or uncontrolled reaction conditions may result in side reactions or degradation of reactants.
• The sodium metal and alkyl halides are dissolved using a dry, aprotic solvent, such as diethyl ether, to avoid undesirable side reactions with moisture.
• Since secondary and tertiary halides can undergo elimination reactions, primary alkyl halides are recommended.

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Wurtz Reaction Mechanism

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Two types of Wurtz reaction mechanisms have been suggested for performing the Wurtz reaction depending upon the conditions.

First Mechanism: By the Formation of Free Radicals as an Intermediate.

​Second Mechanism: Use of an Organometallic Compound as an Intermediate

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Examples of Wurtz Reaction

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The examples of the Wurtz reaction are given below:

(I) Alkyl halide, when treated with sodium metal yields di-alkane, in presence of dry ether medium.

R-X + 2 Na + X-R →R-R + 2 Na-X (Basic Reaction)

• R = alkyl group
• X = halogen (F, Cl, Br, I)

(II) Dry ether is used to provide anhydrous conditions as moisture and sodium metal react strongly in the presence of water. 

Na + H₂O →NaOH + H₂

This reaction produces NaOH that reacts with an alkyl halide in order to produce alcohol. 

R-X + OH^- →R-OH

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Wurtz Fittig Reaction

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Wurtz Fittig reaction is a modification in the Wurtz reaction. The Wurtz reaction in which aryl halides are used in place of alkyl halides is known as the Wurtz Fittig Reaction. This reaction is a very important named reaction in organic chemistry.

 Wurtz Fittig Reaction

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Significance of Wurtz Reaction

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In organic chemistry, the Wurtz reaction is helpful in the production of alkanes. Along with this there are some other applications related to this reaction such as: 

• Wurtz reaction can be easily utilized for the preparation of alkene in laboratory settings. 
• The reaction can also be significant in formation of cyclic structures such as bicyclobutanes. 

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Limitations of Wurtz Reaction

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Some of the limitations of Wurtz Reaction are given below:

• Wurtz reactions have a low yield because of the formation of multiple products.
• Using asymmetric halo-alkanes results in the production of alkane mixtures that are hard to separate. And so, only symmetric alkyl halides are preferred.
• Alkyl free radicals undergo side reactions and form alkene by-products.
• Methane cannot be synthesized by using the Wurtz reaction. Organic coupling reactions must contain atleast two carbon atoms, and this makes Wurtz reaction unsuitable for methane production.
• Tertiary alkyl halides cannot be used in the Wurtz reaction.

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Things to Remember

• Wurtz reaction is a chemical coupling reaction used to synthesize alkanes.
• The reaction takes place in an anhydrous environment.
• Wurtz reaction uses free radicals as an intermediate to induce nucleophilic substitution.
• Asymmetric haloalkanes are not used in the reaction because they produce mixtures of alkanes that are hard to separate.
• Wurtz reactions have a low yield because of the formation of multiple products.
• Tertiary alkyl halides are not used in the Wurtz reaction.

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Previous Year Questions

1. Wurtz reaction is used to unite…
2. Wurtz reaction is not preferred for the preparation of alkanes…
3. Isopropyl bromide on Wurtz reaction gives…
4. Wurtz's reaction involves the reduction of an alkyl halide with… (JCECE 2005)
5. By Wurtz reaction, a mixture of methyl iodide and ethyl iodide gives… (BCECE 2006)
6. The Wurtz-Fittig reaction involves condensation of… (JEE Main 2013)
7. The reaction in which 2 molecules of chlorobenzene reacts with metallic sodium…
8. Which of the following alkane cannot be made in good yield by Wurtz reaction… (NEET 2020)
9. CH₃CH₂Br undergoes Wurtz reaction … (VITEEE 2011)
10. The reagent which can do the conversion CH₃COOH … (KCET 2021)
11. The alkane that gives only one mono-chloro product on chlorination … (NEET 2019)
12. The correct order of boiling points of … (KEAM)